Construction Of Lanthanide Metal-Organic Framework Complexes And Its Sensing Properties

The rapid development of industry has released more and more harmful inorganic ions and toxic organic small molecules into the environment,causing many serious adverse effects on people’s health and life.It’s very important to establish a sensory recognition system for detecting inorganic ions,toxic organic small molecules and nitroaromatic compounds in environmental science,medicine,and life sciences with high sensitivity and low detection limit through visible light emission.Metal-organic-frameworks（MOFs）are new functional materials composed of metal ions and organic ligands,which have an adjustable pore size and a variety of extended structures.Lanthanide metal-organic framework complexes（Ln-MOFs）have a variety of coordination geometries,unique magnetic properties,and high frame stability.They also have unique optical characteristics resulting from the antenna effect,including large Stokes displacement and stability,emission bands,and long luminescence lifetime,making them ideal luminescence sensing materials.The lanthanide metal-organic framework materials（Ln-MOFs）fluorescent probe combines the fluorescence analysis method and the unique optical properties of Ln-MOFs,with the advantage of low sample consumption,fast analysis speed,high sensitivity,low detection limit and real-time detection.In this paper,the lanthanide metal-organic framework complexs（Ln-MOFs,Ln=Sm,Eu,Tb）are designed and constructed.Through fluorescence analysis,the complexes have achieved high sensitivity and low detection limit for multifunctional detection of organic molecules,inorganic ions,drugs,etc.Electrochemical analysis shows that it can be used to detect nitroaromatic compounds.The specific contents are as follows:1.A novel Sm-MOF sensor with molecular formula Na[Sm₆（DBA）₆·5H₃O]（1）has been prepared based on samarium chloride（SmCl₃）and a penta-carboxyl organic ligand（DBA=3,5-di（2’,4’-dicarboxylphenyl）benozoic acid）under solvothermal condition.Complex 1 was characterized by single crystal X-ray diffraction analysis,elemental analysis and thermogravimetric analysis,and powder X-ray diffraction.Structural analysis shows that the dimer metal units are alternately connected into a one-dimensional chain,and the one-dimensional chain is connected by the bridging carboxyl oxygen of the ligand H₅L to form a two-dimensional double-layer plane.The two-layer double-layer plane is coordinated with the Sm³⁺ion by the carboxyl oxygen of the ligand to form a three-dimensional microporous skeleton.Fluorescence studies have shown that Sm-MOF can detect HAc,Ag⁺,cimetidine tablets,MnO₄^-with high sensitivity,and can also be used to electrochemically detect o-nitrophenol in water.The high sensitivity detection capability of complex 1 can enrich the application of rare earth samarium complex in multifunctional sensing materials.2.A novel Eu-MOF sensor with molecular formula[Eu₅（DBA）₃]n（2）has been prepared based on a penta-carboxyl organic ligand（DBA=3,5-di（2’,4’-dicarboxylphenyl）benozoic acid）and europium nitrate under solvothermal condition.Complex 2 was characterized by single-crystal X-ray diffraction analysis,solid fluorescence analysis,elemental analysis and thermogravimetric analysis,adsorption performance analysis,and powder X-ray diffraction analysis.Structural analysis shows that the binuclear and polynuclear inorganic building untis to form stable microporous structure based on the wholly deprotonated DBA ligands.The gas adsorption experiments of N₂ show that complex 2 possesses microporous properties.Fluorescence studies show that Eu-MOF can detect acetone,Cu²⁺and Cr₂O₇^2-with high sensitivity,and can also be used for electrochemical detection of explosive 2,4,6-trinitrophenol（TNP）in water.The high sensitivity and low detection limit detection ability of complex 2 might make it a potential functional sensing material for potential environmental pollutants in the future.3.A novel three-dimensional microporous terbium-organic framework（Tb-MOF）named as[Tb₁₀（DBA）₆（OH）₄（H₂O）₉]（3）,was successfully obtained by solvothermal method based on the terbium nitrate and 3,5-di（2’,4’-dicarboxylphenyl）benozoic acid（H₅DBA）.The complex 3 has been characterized by single crystal X-ray diffraction,elemental analysis,thermogravimetry and fluorescence.Structural analysis shows that there are two kinds of metal species:binuclear and tetranuclear,which are linked by H₅DBA ligands in twoμ₇ high coordination fashions into three-dimensional microporous framework.Fluorescence studies show that the Tb-MOF can detect H₂O₂,Fe³⁺and Cr₂O₇^2-with high sensitivity,and can also be used for electrochemical detection of exposed 2,4,6-trinitrophenylamine（TPA）in water.The high selective and sensitive detection ability of the Tb-MOF might make it a potential functional sensing material in the future.